


in the shadow of your heart

by nilchance



Series: ain't this the life [24]
Category: Undertale (Video Game)
Genre: Accidental Stimulation, Fellcest - Freeform, M/M, Soul Touching, Underfell Papyrus (Undertale), Underfell Sans (Undertale), eventual spicykustard, kustard - Freeform
Language: English
Status: Completed
Published: 2019-04-25
Updated: 2019-04-29
Packaged: 2020-01-31 21:30:12
Rating: Mature
Warnings: No Archive Warnings Apply
Chapters: 2
Words: 14,468
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/18599785
Author URL: https://archiveofourown.org/users/nilchance/pseuds/nilchance
Summary: Edge sees more than he expected.





	1. Chapter 1

**Notes for the Chapter:**

> detailed content warnings in the endnotes

When Edge gets his front door unlocked, it opens on a tableau that he wasn't expecting. 

Red is on Sans's lap, pinning him to the couch, his head bent, his mouth at Sans's throat. Sans has Red's shirt in a death grip, his head thrown back, his expression soft with pleasure. His half-lidded eyes fly open at the sound of the front door opening. In the span of a few seconds, Sans sees Edge frozen there, panics, and plants a hand in the middle of Red’s forehead to shove him off.

“‘Sup,” Sans says as Red sputters, outraged. He’s aiming for casual but his eyes are a little too wide and his grin a little too manic to pull it off. “How’re you, edgelord?”

When Red grudgingly climbs off Sans and flops onto the couch beside him, legs splayed out to take up the maximum amount of room, Edge gets an amazing view of Sans’s shirt collar pulled off his shoulder and the mark on his collarbone in the shape of Red’s teeth, which is already darkening into a bruise. His mind stalls, lost in the way both Red and Sans are rumpled and flushed. Red gives him an infuriating _I know something you don’t know_ smirk.

Sans’s face burns hotter. He pulls his shirt back in place, hiding the bruise, which finally allows Edge the mental resources to speak. He clears his throat and redirects his gaze to the relative safety of the ceiling. There are cobwebs gathering in the corners again. “I left work early. I didn’t mean to interrupt you. Do you want me to go get some coffee and come back?”

“You could always stay and watch,” Red says.

Sans gives him a sharp look, then offers Edge a softer, sheepish grin. “Nah, we’re done. Come on in.”

“I wasn’t done,” Red grumbles. Then he glances down at Edge’s feet and blinks. “Hey, boss?”

Reflexively, Edge looks down just in time to watch the stray rub against his ankle and then stroll into the house like her name is on the lease. He inhales sharply, caught between delight and horror because--

There is a warning growl from the direction of the kitchen table, where Doomfanger is sprawled out over the stack of today’s mail. He watches with his narrowed eye as the interloper moves through the living room, headed towards the kitchen where Doomfanger’s food bowl is. She flicks an interested glance his way and keeps moving as if he surely must be growling at someone else, or perhaps that’s his way of saying hello.

Edge steps towards the incoming collision, leaving the door cracked open in case she needs a quick exit, and Red says, “Let ‘em work it out. It’s gotta happen sometime.”

Frowning, Edge glances at him and Sans, who shrugs but doesn’t look particularly concerned about the twenty pounds of feline murder jumping off the table to land next to the stray. Red has a point; if the stray is going to stay here, then she has to meet Doomfanger at some point. Doomfanger has bloodied the dogs but restrained his killing to what he can eat, and she’s quick enough to survive on the street this long. None of these rationalizations are making him any less tense.

Doomfanger steps into the stray’s path. She pauses, her tail crooked into a question mark, and he leans in to thoroughly sniff her. She returns the favor, whiskers still fully forward even as Doomfanger’s ears slowly begin to flatten. Just as he draws in a breath, no doubt to hiss, the stray breaks the standoff by smacking him in the face.

Strange. Edge never realized she has a death wish.

Edge lunges forward, ready to swoop down and rescue her from Doomfanger’s wrath, but instead Doomfanger goes skittering back. In a few short jumps, he goes from the floor to the kitchen table to Edge’s shoulder and stays there, hissing and spitting. The stray gives him a look that says quite eloquently _dude, what’s your fucking problem?_ and starts grooming the paw she hit him with the same care that Undyne examines her armor after a fight.

Sans and Red (particularly Red, who’s watched Doomfanger frighten Doggo up a tree) burst into laughter. Doomfanger turns his head to hiss directly at them, a sulkier noise.

“Oh love,” Edge says, trying not to laugh so as to preserve some of Doomfanger’s dignity. Reaching up, he starts to smooth down Doomfanger’s fur, particularly his tail, which is bushed out enough to make him resemble a raccoon. “That didn’t go very well, did it? There now, let me see if she drew blood.”

“Scrappy little fucker really doesn’t give a shit,” Red says, his tone admiring. He steals a quick, relatively chaste kiss from Sans when he’s distracted and pulls back to grin at his unimpressed expression. “Remind you of anybody?”

“I’ve never licked my own asshole, so no,” Sans says dryly.

“You licked mine, that’s close enough.” Red gets off the couch and heads for the kitchen, pausing in the doorway when the stray cat just sits right in his path. They assess each other. She doesn’t move, her skittish fear replaced by sheer unintimidated ballsiness now that she’s apparently decided this is her house. Red snorts and steps around her, going to the fridge. A moment later, he pulls something out with a rustle of plastic. “C’mere, killer. Whoever draws first blood gets turkey. House rules.”

As far as Edge can tell, there was no blood drawn. She had her claws retracted when she struck. The only thing wounded is Doomfanger’s pride. Rubbing Doomfanger’s tattered ear, Edge tells Red, “You had best not be teaching my cat to get on the counter, brother. Fang may be a lost cause but there’s still hope for her not to be a spoiled monster.”

“I would never,” Red says in a tone of wounded innocence as he dangles scraps of lunch meat over the counter. The stray jumps up on the counter, snatches the meat out of Red’s hand so fast that it’s amazing he doesn’t lose a finger, and retreats to the furthest corner of the counter to wolf it down. Then she’s back for more, opening her mouth to give a squeaky warcry. Red gives her an entire sandwich-sized portion of turkey at once, which she shakes viciously to snap its non-existent neck and then eviscerates. Red laughs. “Attagirl. You murder the shit out of that.”

“Yeah,” Sans says to Edge. “Totally your cat.”

“Fuck you, sweetheart,” Red says without looking up from what he’s doing, entirely occupied by the stray.

“You say that as if I don’t know he feeds Doomfanger when I’m not looking,” Edge says.

“You’re outta your mind, boss. Told you when you found him in that snowbank that I ain’t gonna feed your fucking hellbeast.”

“Then why did Fang have sashimi breath last night?” Edge asks.

“Sans,” Red says. “He’s a soft touch. It’s sad, really.”

Doomfanger gnaws affectionately on Edge’s fingers for a moment, then jumps down onto the floor with a loud and somewhat graceless thud. Trotting to the kitchen, Doomfanger slams his head into Red’s ankle and yowls a complaint about this unfair treatment. Red tosses him a few pieces of turkey, which Doomfanger snarfles up as the stray peers thoughtfully down at him from her perch. Licking his chops, Doomfanger glares up at the interloper.

Her tail twitches once. Twice. Then she launches herself off the counter and onto Doomfanger, bowling them both over in a tumble of limbs. Before Doomfanger can even growl, she disentangles herself and bolts through the living room, headed for the bedrooms. Doomfanger lays on his side, staring after her, and looks at Edge in utter bewilderment.

Something goes crashing to the floor in the direction of Edge’s bedroom. He winces. The stray trills a noise that he remembers from the first year of Doomfanger’s kittenhood, the sound of a young, healthy cat demanding attention lest they start destroying furniture. Doomfanger’s ears swivel forward, but he stays where he is, watching Edge hopefully.

“Well, go get her, then,” Edge says, trying not to smile.

Another trill from the stray, shading towards a yowl, and Doomfanger tears off after her. There is the sound of a collision of furry bodies, something else hitting the floor, and then the cats streak across the living room and down the stairs to the cellar with a thunder of paws. More thuds from downstairs. There’s no hissing, growling, shattering glass, or wailing like anybody’s being hurt. Edge will check on them in a minute.

“Uh, they’re both fixed, right?” Sans asks.

“She is,” Edge says. “The local catch and release program tattoos the cats they’ve sterilized.” 

Red wanders back in from the kitchen, wiping turkey juice off onto his shorts like an animal. “First time the boss saw a serial code inked onto her belly, he flipped his shit. Thought she escaped from some lab somewhere.”

Sans is still smiling, making eye contact, but the look in his eyes goes strangely guarded. “I figured labs were more into dogs. Y’know, like a laboradory?”

Edge glances at Red. After years of relying on Red’s ability to read people, he doesn’t need to be a judge to see in Red’s expression that yes, he sees it too, and yes, it probably relates to the discussion Edge and Red had last night once Sans went home. Red continues easily, “Pretty sure he was gonna burn the joint down for fucking with his kitten once he figured out where it was. Then he called animal control to demand information, and some poor vet had to talk him down. It was hilarious.”

“That’s kinda sweet, edgelord,” Sans says with a smile that almost touches his eyes. “I mean, aside from the arson.”

Sweet. Flustered, Edge says, “I would’ve made sure that the staff had gone home for the night and my brother had transported the animals out. It would’ve been discreet. I have standards.”

Sans’s smile softens further into something real. “I dunno, buddy. You hang out with us.”

“It has its moments,” Edge says. 

Sans drops his gaze to the floor, grinning. Once again, his hand wanders over to his wrist for no reason that Edge can divine. There’s no bruise there, nothing remarkable. “Aw, flattery will get you everywhere.”

For a moment, Red is dangerously quiet. Edge may have crossed the line into sentimentality, particularly considering that Red’s LV seems to be acting up, and Edge reflexively braces for the outburst. All his brother does after that long silence is roll his eyes and drawl, “Close the fucking door already, boss. You’re letting a draft in, and Sansy’s freezing.”

That slaps Edge back to reality. He doesn’t know what the hell he was thinking to leave a door open instead of safely locked. Red is right, he’s gotten soft. He quickly closes it and throws both locks, then turns back to frown at Sans. “You’re cold again?”

Sans shrugs, which is less than helpful. “No big deal. Felt okay all week, but the symptoms started kicking back up yesterday.”

“Define okay,” Edge says.

Another shrug, this one a little helpless. “‘Bout the same as before I got that fourth crack.”

“Your version of okay is bullshit,” Red puts in somewhat hypocritically. “You were already sick as fuck.”

“Better than I was when I first got back,” Sans says. “It’s relative.”

“You shrug off stuff that would make most people cry for their mamas.” Red drops onto the couch beside Sans and slings a friendly arm around his shoulder. “Why is that?”

“Just lucky, I guess,” Sans says, not seeming particularly concerned about Red being in a position to choke him to death. “You gonna take your jacket off so we can do this, edgelord, or are we playing twenty questions instead? Because I’m more fond of truth or dare.”

Red snorts. “Like hell you’re a fan of anything with the word truth in it.”

“Hey, it’s only that first one that’s the problem,” Sans says, relaxing as Red allows him to change the subject. They make a picture side by side, Red sprawled and claiming more than his fair share of space as always and Sans pulled in on himself, easier to overlook. The better to eavesdrop.

(Or to make himself a smaller target.)

“You’re more of a seven minutes in heaven kind of guy, I think,” Red says to Sans, idly fingering the collarbone he bit. “Although with that mouth of yours, you’re probably not used to it taking longer than three.”

Sans leans his head to the side to give Red better access to touch him; it’s difficult to tell whether he’s conscious of doing so or not. “My average is two, actually.”

Somehow this manages to be worse than when Sans carefully talked around anything to do with sex when Edge was in earshot. At least then Edge didn’t have to deal with the sudden mental image of Sans crowding him into a storage closet and dropping to his knees to show him all things he can do with that clever mouth.

“It _was_ two minutes,” Red says as Edge begins silently undoing his boots because try as he may, he’s unable to make himself do the wise thing and walk away from this conversation. “I threw off your bell curve.”

Sans wobbles his hand from side to side, the wryness of his grin and the look in his eyes contradicting him even as he says, “Yeah, it’s a whole two and a half minutes now.”

“Keep talking shit,” Red says, and his tone is the same wayward fondness he sometimes directs at Edge when he forgets himself. “We’ll see how long you last when I put a vibrator on your--”

Edge clears his throat.

Red grins at him. “What, boss? You got suggestions?”

Looking far less horrified than Edge would’ve expected, Sans mutters something that sounds distinctly like, “Don’t help me.”

Or possibly it’s simply, “Help me.” That would be less cryptic. Either way, it seems like a good time to intervene.

“Enough,” Edge says, giving Sans a look that he hopes conveys his apologies for Red’s goading. Sans gives him a _what can you do_ shrug, unexpectedly laissez faire about something that would have had him ready to bolt a few days ago. Edge finds it equal parts gratifying and unnerving because he has no idea what’s going on behind behind those deceptively sleepy eyes. “I’m going to check on the cats, and then we can start.”

“Okay,” Sans says.

“They’re fine,” Red says dismissively. “Besides, if one of ‘em kills the other one, it cuts the cat food bill in half.”

Edge gives him a withering look. (Red fails to wither.) Then he goes downstairs. There’s no blood trail to follow. That’s a promising start. 

It doesn’t take him long to find them, curled up in a basket of clean laundry that Red naturally didn’t fold or put away when it was done. Doomfanger is on the bottom of the cat-pile, his eye closed in feline contentment as the stray that’s half his size vigorously grooms his broad, scarred head.

When Edge takes a knee beside the basket, the stray pauses to look at him. He offers her his fingers, which she sniffs and then rubs her face against to claim him as hers.

“Well, you certainly seem to have worked out a pecking order,” Edge says. As if she understands, her eyes narrow to smug golden slits. Someone clearly thinks she’s queen of the house now. Someone may not necessarily be wrong. “I suppose we’ll have to come up with a name for you. I didn’t want to presume. Rest assured, it will be neither Death Death nor Zeppelin no matter what those two idiots upstairs say.”

She yawns, showing off her little maw full of surprisingly sharp teeth, and then goes back to grooming Doomfanger’s ear. He is dismissed, evidently. He lingers long enough to stroke Fang’s side a few times so he doesn’t feel neglected, and then returns to the living room.

“-- you fucking with my experimental results,” Sans is saying as Edge takes the last few steps, the tail end of some hushed conversation. When he sees Edge over Red’s shoulder, he gives that lazy grin. “Hey. Did you tuck the kids in?”

“They tucked themselves in.” Edge aims a smack at the back of Red’s head on his way past, which Red dodges despite not even looking in Edge’s direction. “You’re going to have to wash those clothes again. How many times must I tell you to put the laundry away instead of shoving it in a basket to wrinkle?”

“I dunno,” Red says. “However many times it takes you to realize I don’t give a shit.”

It’s an old argument that Edge doesn’t feel like having yet again, particularly since he knows the laundry will be rewashed no matter how much Red bitches about it. He sits on the couch on Sans’s other side, careful to give him room, and feels that ridiculous bloom of warmth in his soul when Sans deliberately shifts over so that their knees are touching. Overcompensating for that moment of tenderness makes him sound a little gruff when he asks, “Are you ready to start?”

“If it means Red stops talking,” Sans says, giving Edge a crooked grin that brings him into the joke.

“Good luck with that, sweetheart.” Red undrapes himself from Sans. With one move that reminds Edge that his brother is much stronger than he looks, Red hauls Sans closer, nearly on his lap. Sans’s breath hitches, an almost inaudible noise that causes a flare of heat at the base of Edge’s pelvis. Red props his chin on Sans, the proverbial devil on his shoulder, and grins at Edge. “I don’t come with an off switch.”

“Don’t I know it,” Sans says, but he doesn’t try to squirm out of Red’s grip to reclaim a little breathing room. “Okay, handsy, do me a solid and do the soul thing. I’m still trying to figure that trick out.”

That slaps the smugness off Red’s face. They all know he’s struggling with his LV, and he clearly wasn’t expecting for Sans to literally put his life in his hands right now. He turns his head to look at Sans, who looks evenly back, a challenge in the crook of his brow. Red squints at him, then grumbles, “Lazy bastard.”

A moment later, Sans’s soul pushes out of his chest. It’s not particularly gentle, but it’s not careless either. Sans doesn’t flinch. He takes his soul in his cupped hands, discomfort in his expression like he’s touching something unclean. Edge wonders if he had this much distaste for his soul before it began to break. Probably. Sans’s self-loathing runs deep.

As careful as Sans isn’t, Edge brackets Sans’s hands with his own. Sans’s expression eases into something softer. Welcoming. The world takes a breath, and for a moment, everything is eclipsed but Sans’s hands cradled in his, Red’s amused eyelights, the soft light of Sans’s soul, the utter satisfaction in Red’s grin.

It passes like a fever, leaving Edge dizzy. Sans breaks eye contact and grins ruefully at the floor. “So,” he says. “Come here often?”

That comment addresses the elephant in the room far more than Edge would’ve expected. A joke to allow the moment to pass, leaving him a little of his dignity.

“I live here,” Edge says, gathering his scattered wits. Red snickers. Both of them must’ve seen every moment of that written on Edge’s face, which makes him feel as vulnerable as if it’s his soul that’s bared. “May I continue?”

Like the last two times, he sees Sans hesitate. It’s no small thing for someone as protective of his secrets as Sans to let anyone in his head. Then he stretches his neck from side to side like a fighter getting ready to enter the ring, sighs and says, “Sure. Why the hell not?”

Smartass. When Sans closes his eyes, Edge takes a moment to clear his mind before carefully laying two fingers on Sans’s soul.

He notices two things at once. First, Sans’s emotions are locked up as tight as they can be, and he’s trying to radiate unruffled nonchalance. It’s like someone trying to lie in a language they don’t actually speak. If Sans’s emotions could whistle innocently, they probably would. Second, Sans’s soul isn’t as parched as it was the first time they did this, still painfully dry but softer beneath his fingers.

Sans looks disconcerted, and Edge immediately breaks contact. “Does that hurt?”

“No,” Sans says after a moment of consideration, eyes still closed. “It’s just weird. Manageably weird, though. Keep going.”

Red meets Edge’s eyes and signs _sensitive_. Because that’s exactly what Edge needs to be thinking of right at the moment that he touches Sans again, whether the fact that Sans feels a simple touch so acutely means that one day, when he’s recovered enough, stroking his soul will completely undo him.

Edge loves his brother dearly, but sometimes he thinks Red could do with a day’s vacation with the pack of wolves that clearly raised him.

“Knock it off, asshole,” Sans says without opening his eyes.

“Hey, I didn’t say a goddamn thing,” Red says, all affronted dignity. How dare Sans accuse him of doing something that he was absolutely doing.

“Technically true, but I can feel your hands moving. Don’t make me turn this soul train around,” Sans says. He’s relaxing into the familiarity of sniping at Red, losing focus on trying to keep Edge at arm’s length. Edge takes the opportunity to begin feeding magic into Sans’s soul, and Sans’s attention jerks back to him with a spike of alarm so sharp that Edge pauses. Sans gives him a nervous grin. “S’okay, edgelord. You’re doing fine.”

Clearly not. 

Gently, Edge says, “Relax. If you’re worried that I’m going to see something you don’t want me to, it’s all right. I might get flashes, images without context, but I’m not going to pry deeper. I give you my word I won’t go chasing rabbits.”

“No, I know,” Sans says, still projecting _nothing to see here_ as hard as he possibly can. “I’m good. Seriously, it’s fine.”

Even as Edge takes him at his word and continues, he glances at Red and raises an eyebrow in silent question.

“You’re a fucking nerd,” Red says. The angle of his grin says that he knows exactly what Sans’s problem is and finds it hilarious, which does not necessarily mean that it’s harmless. He fingerspells _nbd_.

All right, then. Edge’ll have to take his word for it. Watching Sans relax back into Red as he listens to them bicker amiably, or as amiable as they get, Edge says, “I was referencing a literary classic that you read to me when I was a child, not a movie that I’ve caught you watching no less than five times.”

“Go get back in that locker somebody shoved you in,” Red says.

“Big talk considering that the quantum physics department is the universe’s locker,” Sans says. The words are fuzzy around the edges. Hearing himself, he jerks back to full consciousness with another jolt of alarm that he tries to smother with false calm. 

Trying to keep fully alert and out of subspace, perhaps. If anyone could shrug off magic infused directly into his soul out of the desperate need to keep control of himself, it’d be… well, Edge, most likely, but Sans is up there in the ranks.

Repeatedly being told to relax is more annoying than relaxing. Edge takes a deep breath, trying to project calm, patient competence. It’s fine. Red was much worse at first, an erratic mess of desperate yearning for comfort and the viciousness of an animal with its foot in a trap. He can handle Sans rebounding like a yoyo every time he relaxes.

Red studies him, then asks Sans, “Hey, what’s the first law of thermodynamics?”

That makes Sans open his eyes, craning his head back to look at Red. “Why, did you forget?”

“First of all, fuck you,” Red says. “Second, you’re trying not to think about stuff so he doesn’t see it, and that ain’t gonna work. You overthink goddamn everything. We both suck at that ‘clear your mind’ meditation crap. So focus on something you know like the back of your hand. Worked for me when me and him started doing this.”

“I know far more about how to determine the inductance of a cylindrical air core than I’d care to,” Edge says dryly.

Sans gives him a bemused look like he can’t imagine why Edge wouldn’t want to know that clearly critical information, then glances at the magic pouring off his soul and exhales. Settling back in Red’s arms, he closes his eyes again. “The change in internal energy is equal to the heat absorbed by the system plus the work being done on the system. Give me a hard one next time. This isn’t middle school.”

“All right,” Red says, meeting Edge’s eyes over Sans’s shoulder. _Do your fucking job already, boss,_ that look says. “Bernoulli’s Equation.”

“Still too easy,” Sans says. “Incompressible fluid or compressible?”

Edge bends his head over his work. As Sans lets himself be distracted, his pulse steadies beneath Edge’s careful touch. He accepts more of Edge’s magic, his soul soaking it up like rain on dry, cracked soil. His skittish thoughts quiet, replaced by the structured simplicity of formulas and numbers, a white noise muffling whatever he doesn’t want Edge to see.

Absently, he listens to them as Red tsks. “C’mon, sweetheart, you’re always supposed to assume incompressible with Bernoulli’s Equation unless somebody says otherwise.”

“Like you wouldn’t make it a trick question just to be a dick,” Sans says. “Fine. Static pressure plus dynamic pressure equals total pressure.” 

“Funny, I don’t remember asking for the simplified version they give little baby undergrads.”

“I wanted you to be able to keep up.”

“You’re stalling.”

Sans heaves a sigh. “Bernoulli’s Equation,” he begins, sounding like a tired teacher who isn’t getting paid enough to put up with this, and then carries on from there. The edges of Sans’s words have gotten slightly blurry again, but he doesn’t immediately yank himself back to alertness. 

Good enough. Edge tunes them out at that point and concentrates on keeping his own mind clear as he pours magic into Sans. He can’t afford to be distracted.

For all that he’s done this twice before, each experience has been wildly different. Sans’s mind when he was dying was a jagged landscape of shame and fear. Last time it was hazy with weed, a watercolor impression softening but not erasing the agony beneath it. Now the false calm Sans threw up as a smokescreen settles like silt to the bottom of a river, and Edge can see the pain, duller than it was but very much still present, and the clockwork gears of Sans’s restless thoughts gradually slowing from frantic to something calmer, measured, deliberate. 

Thinking is safer than feeling, as far as Red and Sans are concerned. There’s a vulnerable emotional heart at the center of this scaffold of rational thought. Edge leaves it be.

More and more of his magic penetrates the surface of Sans’s soul instead of shoved reflexively back at him, defenses yielding. Though Edge isn’t listening to the words, he can hear that the pauses between Red’s questions and Sans’s answers are getting longer. 

Silver fluid is beginning to well up beneath Edge’s fingers, coating the surface of Sans’s soul like honey. He keeps his hand absolutely still, the resulting tension in his wrist painful but nothing he can’t bear. He keeps his mind clear even as that fluid begins to fall in hot droplets onto their joined hands. He is concentrating so fucking hard on thinking of nothing that it takes him several minutes to realize that the room has long gone silent.

No. Not fully silent. Red is purring again, quiet and steady. The sound makes Edge’s soul squeeze hard in his chest. When he glances up, he finds Red watching him, his expression hard to read. It’s gone in a blink, replaced by a wickedly suggestive grin, leaving Edge to wonder if he hallucinated the soft look in his eyes.

Nothing good can come of listening to Red talk shit right now. Pointedly, Edge returns his gaze to Sans’s soul. (Red was right; it is pretty.) He is in the middle of this uphill sprint, not feeling any strain or fatigue. Soon he will be, very soon, but not yet. He has time. He clears his mind and--

There is a cascade of sensory input, intense and undeniable as a migraine. The wet snap of a finger breaking. White lights glaring off of cold metal tables. The stink of bleach and sickness and acrid sweat. The shaky breathing of someone in pain trying desperately not to make a sound. A child’s horrified voice, crying out that brother, you said--

Edge resets his thoughts with the same ferocity that Red smacks the snooze button every morning. He forces himself to stop, to remember that he’s in their living room on the surface, sitting on a couch that smells faintly of pot smoke. He lets the memory go. He gave his word that he wouldn’t pry.

The flow of his magic must’ve stuttered. Sans stirs, making a muzzy, questioning noise. When he shifts, his soul moves beneath Edge’s fingers, a slick glide, and Sans’s breath catches. It isn’t pain.

Edge freezes in place. Abruptly breaking the connection and leaving Sans alone in his head would be a hell of a shock to the system, so he resists the impulse to yank his hand back like he was scalded. (He resists the temptation to stroke him again, slower, savoring it.) He tries to keep his mind empty, praying that Sans doesn’t do that again, and risks glancing at Red. Surprisingly, his brother doesn’t look smug about this turn of events; his eyes are narrow, demanding an explanation for what just happened.

Edge shakes his head. They’ll talk about it later. Grudgingly, Red nods.

He’s distracted, his mind a jumble of conflicting emotions. Hardly a calm, steady presence in Sans’s head. It’s no surprise when Sans cracks an eye open to look at him, his eyelight hazy, and mumbles, “Edge?”

“It’s fine.” Trying to concentrate is a lost cause. Edge lets his magic peter out to nothing, then breaks contact with Sans’s soul. The inside of his head feels too quiet without Sans there. “My fingers slipped. I’m sorry.”

Sans blinks at him. He’s clearly feeling no pain, his body pliant, but he doesn’t seem quite as out of it as the first two times they did this. Just deeply relaxed and gently bemused by life in general, as laid back as he always pretends to be. “S’okay. Didn’t hurt.”

“Good,” Edge says.

There is a moment of awkward silence. Awkward for Edge, at least. Sans seems immune, and Red is too busy smirking at Edge over Sans’s shoulder. Apparently _now_ Red is going to be smug about Edge inadvertently stroking Sans’s soul; he just delayed it for a few minutes for maximum annoyance.

“You two are a fucking car wreck,” Red says. Just like last time, he takes Sans by the chin and turns his head to get a good look at his face, deeply pleased by what he sees. “Hey, pretty. You good?”

“Are you gonna do this every time?” Sans asks.

“Which part?” Red asks. “The part where I loan you my lap, or the part where I give a shit about how you’re doing?”

“Both.”

“Probably,” Red says. “If you’re cool with it.”

Sans studies him. “Why? Seems boring.”

“I like to watch,” Red says, leering. Sans snorts, and Red lets him go. “Lemme put your soul back.”

The soul lifts out of Sans’s hands, still lazily dripping silver. Sans makes no move to take his hands out of Edge’s even once the soul passes through his shirt and is hidden from sight. Edge looks down at Sans’s hands; he’s never stopped to really look at them before. 

The ring finger of Sans’s right hand is slightly crooked. A broken bone that healed badly.

The first time he touched Sans’s soul, it showed him a broken phalange. He was distracted at the time by Sans dying, and like a fool, he’d let it slip his mind. He hadn’t looked. Careless.

It doesn’t matter. What matters is that he’s looking now.

Edge glances at Sans, who is still studying Red’s face like it’s a fascinating cypher, and then withdraws his hands. Sans turns to look sleepily at him, frowning at his expression. “What’s wrong?”

They can’t keep putting this conversation off. If Edge were to press him for answers when he doesn’t have his guard up, still vulnerable from the intensity and the intimacy of what they’ve just done, it would eliminate a lot of bullshit. Given the caliber of secrets he tends to keep, Sans would understand his reasoning and might even forgive him for it. But he would never trust Edge like this again.

“I realized a problem I have to handle later,” Edge says, meeting his brother’s eyes.

Red sees his anger. His brows raise, and then he sinks back into the couch. He’ll abide, that expression says, but Edge better give him some goddamn information soon. That’s fine. Soon enough they’re both going to find out what they need to know.

“That’s cryptic. Work stuff?” Sans asks, watching him with bleary-eyed suspicion.

“Of a sort.” Edge offers him a smile. Once they have the full story, it’ll come down to the kind of work Edge used to do for Asgore. Blood and dust spilled across the floor. “But when the time comes to deal with it, I think it’ll be my pleasure.”

**Notes for the Chapter:**

> Content warnings: Edge walks in on Sans and Red making out, flashback to medical abuse, Edge inadvertently strokes Sans's soul and Sans likes it, Edge considers and discards the idea of Sans being out of it to get information, Edge thinks about murdering Gaster
> 
> tfw you're trying to keep your crush from seeing that you have the hots for him and you accidentally reveal your childhood trauma instead


	2. Chapter 2

**Summary for the Chapter:**

> Sans makes a point.

**Notes for the Chapter:**

> detailed content warnings in the endnotes
> 
> (Seriously, this chapter gets into some rough content, so please check if you think you might need to.)

Just before Gaster’s fingers close around his soul, the void lets Sans go. He can move again. He comes up fighting with all the blind panic he has. Someone is touching him, a hand on his shoulder. Bone white mask, dark clothes, cracked eye. He grabs their soul and shoves them back, scrambling backwards to get away only to hit some barrier. Gaster is still too close, too fucking close, and he’s too terrified to look away to find a better escape route. Even when the attack hits him square in the chest, Gaster only rocks back a few inches and says, “Sans, you’re all right. You’re safe.”

Even if he did use his voice to speak, Gaster wouldn’t sound that gentle.

Edge. Sans is in their living room, not the lab. He fell asleep after Edge healed him, he had a stupid nightmare, and he just fucking stabbed Edge in the chest. 

Seeing that Sans finally recognizes him, Edge turns his attention to pulling the attack out before it can continue to do more damage. It bounces harmlessly off the carpet, crackling faintly before it crumbles into dust. Edge’s HP is still ticking down, KR burning livid in the wound. Sans was aiming for his soul, but he missed by a mile, thank fuck. Edge is bleeding but not dying, he’s got all that HP to spare, but--

“Red,” Sans says hoarsely. His throat hurts. “Where--?”

“Got out of firing range when you started freaking out,” Red says from behind him. Sans flinches hard, his head snapping around, and Red gives him a little finger wave from where he’s leaning against the fridge. The corner of his eyes are tight, and his neutral grin is as good as a frown. “That was a nice shot.”

Red’s pissed. That’s understandable. Sans is pretty fucking pissed at himself. He turns back to Edge, who has pulled a handkerchief out of some pocket and is holding it to the wound. Sans has never been squeamish about his own blood, but the sight of Edge’s makes his head swim. With shaky hands, he pulls a juicebox out of his inventory and pushes it at Edge. “Sorry. I’m so fucking sorry, edgelord.”

There’s no anger written on Edge’s face as he takes the juicebox. If anything, he looks haunted. Red told him once that Asgore used to force Edge to torture him. It may not have been the stabbing that rattled Edge; it may have been the screaming.

After taking a sip, probably more to reassure Sans than anything, Edge says, “I’m fine. No apology necessary. I know better than to try to wake someone from a nightmare by touching them.”

“Yeah, that was a real dipshit move,” Red chimes in. “I’d have stabbed him too.”

“It’d be an improvement over forcing me to evade your blasters at three o’clock in the fucking morning,” Edge says.

“Then quit watching me sleep, you creepy little asshole,” Red says. 

Sans isn’t sure which of them is supposed to be put at ease by this impromptu round of bickering, but it seems to be working for Edge. Some of that dangerous tension is easing out of him with every annoying word out of Red’s mouth. Red’s version of reassurance: _I’m not too hurt to be a dick. I’m fine. We’re fine._

“I’m two feet taller than you,” Edge says. Red flips him off. To Sans, Edge adds, “And he’s right. I think your karmic retribution does more damage. It’s interesting.”

“He’s got lower LV,” Red says. “Might be that’s got something to do with it. Inversely proportional to KR and shit.”

“Perhaps,” Edge says, not even a little fussed about the fact that Sans just shanked him. It adds a surreal tilt to the situation that Sans really doesn’t need right now.

Sans presses his palms to his eyes for a second, trying to get it together, trying to get his soul to quit pounding and his hands to stop shaking. Not a smart idea. The memory of that claustrophobic darkness is still too close. He drops his hands and decides to stare at the nice, safe couch cushions instead.

“Uh, sorry about the screaming,” Sans says when he thinks he can sound like he’s not having a panic attack. The fuzzy, comforting warmth of having his soul touched is gone, leaving him stone-cold sober and awake. “Heh. I mean, I guess even if you did have neighbors, they’d have heard worse, but. Yeah. Awkward.”

There’s a quiet moment where he’s pretty sure Red and Edge are exchanging significant looks, but damned if he’s glancing up to check. Then Red says, “You done freaking out so I can sit down?”

Still freaking out, but not to the tune of stabbing anybody, Sans nods, his fingers drifting to his wrist. His bare wrist. He took the collar off before Edge got home, stashing it in his inventory. (Red gave him dark looks all night but didn’t actually say anything about it, so it was fine.) No wonder he had that fucking nightmare. He hadn’t meant to doze off, but he’d been so comfortable, if not quite as out of it as last time, and Red had been so warm to lay on, and…

“I oughta get going, actually,” Sans says. “Hate to stab and run, but--”

“Move over,” Red says in a tone that brooks no argument. _You just stabbed my brother, so don’t fuck with me,_ that voice says. So Sans moves over, and Edge makes space for him between them. The couch dips beneath Red’s weight. Casually, he says, “So what’d he do?”

Sans stiffens, which is as good as a flashing neon sign announcing that Red hit his mark. In some last desperate hope that he can avoid this trainwreck, he says, “I dunno who you’re talking about, buddy. You’ve gotta narrow that down.”

“I would, sweetheart, but you get real twitchy when I say his name,” Red says. “Let’s try to avoid catching his attention if we can help it, huh?”

Sans isn’t ready for this. He already told Papyrus, isn’t that enough? Can’t that be enough? He doesn’t want to drag this corpse up into the light again for people to poke it with sticks. He lived this whole ugly clusterfuck already, and he’s the one that has to remember, and--

And it was his fault to begin with. So. There’s that to counterbalance his fucking self-pity.

“Last night me and my bro were comparing notes. I know about the part where the doc decided to send you two to our universe,” Red says into his silence. “Sure, maybe it was because he wanted to see what happened. He was an asshole like that. But it kinda sounds like he has a grudge. I know he fell in the Core. I know you flinched back in that alley when I said the only reason you didn’t have LV was a technicality. So I think maybe he didn’t fall into the Core ‘cause he tripped.”

“I didn’t push him, if that’s what you’re asking,” Sans says. 

“Coulda saved him, though,” Red says. “You got the same kind of magic I do. You let him drop.”

It’s not a question. It doesn’t need an answer. Sans looks down at his hand, the crooked finger, and keeps his mouth shut.

“You ain’t the kind of person who woulda done that for shits and giggles,” Red says. “You’re not me. And you’re fucking terrified of him. I got that much even before you started screaming in your sleep like you were being tortured. So seriously, Sansy. Level with me. What’d he do?”

On the surface, Red sounds calm. Friendly, even. Just two pals having a little chat. Which means he’s probably angry enough to kill somebody over this, and he wouldn’t do it quickly.

Sans raises his eyes to Edge’s face, a silent plea to call Red off. Edge meets his gaze with an expression that establishes the fine distinction between sympathy and mercy. He’s sorry Sans is hurting, that look says, but he’s not going to stop this.

“You weren’t just screaming,” Red says. There’s a cold, cold fury underneath his easy tone, the same that was there when he saw the bruises Unundyne left around Sans’s throat. Worse. “You begged him to stop. You said you were sorry. It sounded like he was--”

“It wasn’t like that,” Sans says. 

Just like that, he’s showed his hand. Hilarious that what finally exposes him is the kneejerk instinct to defend Gaster. But it’s true, Gaster didn’t rape them. He didn’t beat them. He didn’t hide that he found the idea of touching them at all disgusting. All he used were words, and Sans stuck his arm out for the needle, swallowed the latest cocktail of pills, and behaved.

There’s a creak of springs as Red leans forward in his seat, smelling blood in the water. Ruthlessly, he asks, “Then what was it like?”

Ha. Sure, just put into words six years in that cold, sterile lab, trying to not to catch Gaster’s notice. Learning not to show pain because all it would do is upset Papyrus. Patching his brother’s burns and trying so fucking hard not to be furious with him for volunteering to be tortured for his sake. The days and weeks of puking, seizing, burning in a haze of fever as Gaster tinkered endlessly with his drug regimen. Waking up, remembering where he was, and sometimes entertaining that flash of guilty hope that maybe this round of pills would just kill him so he didn’t have to take this bullshit more.

Red and Edge didn’t talk about the place where they came from, but if they had, it wouldn’t have explained anything. Sans wouldn’t have understood until he was there, tasting dust in the air and living with the constant weight of fear and dread. Even now, he still doesn’t get what it was like to grow up steeped in that. Words don’t explain any better than his notes on the resets make him remember how it felt to grieve for his brother, Undyne, Toriel, his entire fucking world.

It’s one thing to tell Papyrus, who was there even if he can’t remember, who forgives him even if he shouldn’t. It’s another to say it to Red, who killed or fucked strangers to keep Edge safe and fed, or to Edge, who thinks Sans is something better than he actually is.

He tries to speak. The years are clogged up in his throat. He tastes metal and the sickly sweet fluid Gaster put in the feeding tube. He closes his eyes, swallowing hard against sudden bile, and flinches when Red puts a warm, steadying hand on the back of his neck.

Even with Red’s LV riding him, if Sans got up and walked out, they would let him leave. But the cat’s out of the bag now. Gaster fucked with Edge. Red’s not going to let Sans keep them in the dark forever.

“See, the Core wasn’t the only thing the doc did for Asgore,” Red says. “When I judged somebody, they didn’t go get rehabilitated in a nice room with nice people until they decided to play nice too. Sometimes he gave them to the doc to play with. You can learn all sorts of shit if you don’t worry about ethics.”

Sans’s breath shudders out. He doesn’t take another one, just sits there and is as silent as he can be, trying to disappear from this room. Red doesn’t need him here; he’s got it mostly figured out. Sans is irrelevant. Edge reaches out and takes his hand, and for a moment, it’s like it’s happening to someone else. It has nothing to do with Sans, this hand that’s limp in Edge’s grip. 

Then he latches on suddenly and too hard, like he’d hold onto a rope out of the void. Edge doesn’t protest. He still hasn’t put his gloves back on, his bones hot against Sans’s icy ones.

“Your king doesn’t play like that,” Red says, stroking Sans’s spine where the collar would rest. Fuck, Sans wants the collar. “He wouldn’t hand prisoners over to be experimented on. I figured maybe your doc was a soft touch too. Guess I bought into all your crap about things being different here. You played me like a fucking rube.” 

Sans wouldn’t have thought he could get any more tense, but that ratchets his adrenaline up even more. If Red flips his shit right now, Sans doesn’t know if he can take it.

“Ain’t you I’m pissed at, dipshit,” Red says. Apparently he doesn’t need to see Sans’s face to know what he’s thinking, just his body language. Then again, he knows Sans’s body very, very well. “One con artist to another, I’m impressed. But the jig’s pretty damn up at this point, so how about you tell me how you ended up the one on the doc’s table? Blackmail? Did he make it a condition of employment or something?”

Sans laughs. It’s a little crazy, loud enough that it puts cracks in his brittle calm. He can feel both of them go still, Edge’s fingers tightening briefly on Sans’s. Maybe Edge heard the way Sans laughed when Unundyne found him in Asgore’s dust and he doesn’t like the similarities.

That one laugh jostled Sans’s words free from the knot in his throat. He says, “You were on a roll for a while there, Columbo. Close but no cigar.”

“Welp, fuck me, I guess,” Red says. Can’t fault his speed of recovery. “Good thing I don’t like cigars.”

“No, you smoke menthols, you fucking heathen.” Sans sighs. “I could really use a cigarette.”

“Open the window, brother.” It’s the first thing Edge has said for a while, startling Sans into meeting his eyes for a second before the compassion in them makes him look down at their joined hands again. Edge squeezes his fingers gently. “For once, yes, you can smoke cigarettes in the house. Don’t make it a habit.”

Red pats the back of his neck and then takes his hand away, leaving Sans cold. A moment later, Sans can hear him unlocking the window and yanking it open, grumbling as it sticks a little. It’s not until Red is back that Sans realizes that he probably should let go of Edge and retrieve his smokes from his discarded jacket, but Red is already lighting a cigarette and holding it out to him, like some kind of nicotine miracle.

Edge releases Sans’s hand to let him grab the cigarette, but Sans holds on and takes it with his right. He’s ambidextrous with cigarettes and handjobs, it’s fine. When he takes a drag, he doesn’t even care that it’s menthol. He’s not proud. 

He sits there for a second, smoke seething from his eye sockets and under his shirt collar, and then exhales the smoke along with the truth. His voice is emotionless. “You already know we lived on the street for a while. The doc came along one day. Offered me food and to let us crash in the lab in exchange for a couple tests on me here and there. Seemed like a good deal. It sucked. I could’ve taken Paps and walked out at any time. I didn’t. Eventually Paps volunteered for tests too. That sucked more. Then I got a real job, we moved out and it was done. End of story.”

“How old were you?” Red asks.

“That’s not really relevant.”

“Because you’re so fucking good at deciding what information might be a teensy bit relevant before it blows up in everybody’s face,” Red says, an edge to his voice.

Sans winces. Edge says, a tug on the leash, “That’s unnecessary.”

“No, he’s got a point.” Sans glances around for somewhere to put the ash that’s slowly gathering at the end of the cigarette, and Red deposits an ashtray on his knee. He occupies himself with that for a minute, long enough that Red draws in a breath to prod him again, before he says, “I was nearly out of stripes. Old enough to know better.”

“Twelve,” Red says, his voice dangerously flat.

Edge’s silence is very loud.

“Almost thirteen,” Sans says. By Gaster’s estimation, anyway, although age is a tricky thing to guess based on determination readings, marrow samples and skeletal growth. Long-term food deprivation and Sans’s shitty HP threw the numbers off too. It’s promising that Red came to the same conclusions about what age they all are, but the standard deviation is probably three years or more.

“ _Twelve_ ,” Red repeats, his voice harder. Sans shrugs. “How old was Paps when the doc started with him?”

“Ten,” Sans says heavily. It’s burned into his brain, how little Papyrus was when he took Sans’s hand and told him that it was going to be okay now. They were doing this together.

The couch rocks violently with the force of Red getting up. Sans keeps himself from flinching again somehow, watching Red start to pace like a tiger testing the limits of its cage. Edge turns to Red and says very quietly, “Brother.”

“Just gimme a fucking minute!” Red snarls.

This is the worst possible time for them to be having this conversation. Red was already on the verge of another freakout, and Sans is tossing jet fuel on the fire. He looks at Red, the trembling tension in his body like a wire about to snap, and then a little helplessly at Edge. 

Sans thought he had seen Edge angry before, that night that he bounced Red off a wall. It had been intense, a quick and loud firestorm that scared the shit out of him. But it’s nothing compared to the look in Edge’s eyes now. That’s the kind of fire that can burn as long as it needs to, the kind that leaves nothing standing when it’s done. 

That expression gentles as Edge looks at Sans. “It’s all right.”

He extricates his hand from Sans’s and gets off the couch to join Red. When Edge touches his shoulder, Red jerks, turning on him, his eyes black pits in his face. Before Red can spit venom, Edge murmurs something Sans can’t hear. Red stares at him, his breathing slowing. Edge says something else, his voice lulling even as his eyes burn with that apocalyptic fury, and after a moment, Red’s answering grin is slow and vicious.

Sans isn’t afraid of their anger. He’s afraid for them.

“I made the deal,” Sans says. They both turn to him, looking more like brothers than they ever have. “I stayed. I kept Paps there. The doc is a fucking asshole, but my hands aren’t exactly clean here, so don’t--”

“Goddamn, he really did a number on you,” Red says, his eyes searching Sans’s face with something close to wonder. “It wasn’t bad enough that he used you as a lab rat. He fucked with your head until you thought the cage door was unlocked.”

Sudden anger stabs through Sans, as if his guilt is something Red is trying to pry out of his hands. “Okay, now you’re ignoring everything that doesn’t fit your little theory. We could leave whenever we wanted.”

Red comes back to the couch and sits. He’s still seething, violence radiating off him like heat waves off blacktop in the summer, but he seems less likely to explode. “Where were you gonna go, huh? Back on the street to starve? To the guard, when he was the king’s right hand and the last time you tried to trust somebody, it blew up in your face? Sure, I can see you had a lot of options, sweetheart.”

“You didn’t starve,” Sans says. “We would’ve been fine.”

Red laughs, an ugly sound. “Oh yeah, we did _real_ fine. My little brother killed people, I sucked dick to get by.” Out of the corner of his eye, Sans sees Edge wince. “It was great all around. Face it, Sansy. You were fucked either way. Get pissed at the right person.”

Grinding his cigarette into the ashtray, Sans asks quietly, “You think I’m not angry?”

“Hell no, you’re furious,” Red says. “You’re angry at the whole damn world, but that never changed a fucking thing. So you just choke it back and hate yourself instead. And when all that pain starts to break your soul, you don’t say a word because you don’t really give a shit anymore if it kills you. No big loss, right?”

“Oh, screw you,” Sans says, more vicious than he means to be, but Red just cracked his ribcage open and poked around inside so he thinks he’s a little goddamn entitled. “You should fucking talk.”

“Been there, done that, got the t-shirt. Turns out it works better if you take the shotgun out from under your chin and point it in the other direction.” Red nods down at the ashtray in Sans’s lap. “Pretty sure that cigarette is already as dead as it gets.”

Sans realizes that he’s still grinding the cigarette out. The paper split, and there’s tobacco leaves scattered everywhere. Disgusted, he lets it go.

“You want another one?” Red asks, as if they’re having a totally normal conversation. 

Jerkily, Sans nods.

As Red starts to extract a cigarette from the pack, he says, “You’re awful quiet over there, boss.”

“You had a great deal to say,” Edge says neutrally. “As always.”

He returns to the couch, bare feet silent on the carpet, and pauses to briefly rest his hand on the back of Red’s neck. Then he sits down beside Sans again. Just having him there makes Sans feel steadier. Safer. One for the experimental results, apparently. Edge puts his hand on Sans’s back, a bracing touch, and Sans realizes that he’s gone as wire tense as Red was.

He accepts the cigarette Red hands him and takes a drag he doesn’t taste. Gradually, he forces himself to relax.

“I got another question for you,” Red says.

Sans laughs, humorless. “Of course you do.”

“You don’t gotta answer,” Red says. “This time around, you can actually leave.”

Sans sighs, rubbing his brow. “I’m already here. Get it out of your system.”

“Did Asgore know?” Red asks.

When Sans looks at him, he can see that if Asgore knew, Red will kill him no matter what the consequences are. A quick glance at Edge tells him that Edge would help sweep up the dust when it was done.

“No,” Sans says. “He had no idea. The big guy’s got a lot of faults, but he wouldn’t stand for that.”

Red exchanges a look with Edge, a silent confirmation that Sans is telling the truth. Edge nods, relaxing a little, and Red continues, “What kind of experiments? He had a whole slew of them back home, but those mostly involved people dying one way or another.”

“He was trying to make Paps better at fighting. Training regimens. Traps and puzzles. Paps used to call it lasers and razors.” Remembering Papyrus’s wobbly, brave smile when he says it hurts like a kick in the chest. “I think the doc was planning to start making… adjustments when he got out of puberty, but we were out of there by then.”

“Good,” Red says, a protective growl. 

“Finally, something we can agree on,” Sans says.

“And you?” Edge asks.

“He wanted to make permanently raise my HP without me having to, y’know, kill people.” Sans gestures vaguely at himself. “You can see how well that worked.”

“Raise it?” Red asks, a furrow between his brows.

“How?” Edge asks.

“Little bit of this, little bit of that. He tried this thing where he shoved a feeding tube down my throat and--” Sans’s voice shakes on the last word. This is old news. It doesn’t even matter anymore. He pauses to smoke a little before he continues, steady as a rock, “That worked to keep things stable when he caused limited amounts of damage. At least enough that when he needed a marrow sample, it wouldn’t outright kill me.”

The feeding tube had limited applications. To avoid any unfortunate accidents, Gaster made sure any damage he did was done slow. Decimal point by decimal point. Sans still remembers the needle slowly boring through his iliac crest as he gripped the edges of the table in his sweating hands, knowing any sudden moves would kill him, knowing any noises he made would only piss the doctor off and make the next time worse, staring into the blinding overhead lights and trying not to choke on snot and tears--

“Sans,” Edge says, breaking through to him. It’s not the first time he said it.

Sans takes another drag on a cigarette that seems much shorter than it was the last time he paid attention. That’s the trouble with thinking about this shit. He starts remembering things it’s taken him a long time to forget. What the hell was he saying? Oh. Right. “That wasn’t what he was looking for, though. He passed that onto the medical school and moved onto drugs.”

“What drugs?” Red asks. 

There’s a strange note in his voice that makes Sans turn to look at him. “Dunno. He said answering questions wasn’t part of the deal. It was meds roulette for five years. I couldn’t keep track. Why?”

“Our doc wasn’t interested in raising HP,” Red says. “All the experiments he was doing were about causing damage, not fixing it.”

“That kind of sums up your universe,” Sans says. “Not a lot of altruism over there as far as I could see.”

“The hell with altruism,” Red says. “Something that could permanently jack up your HP without having to deal with LV would be really handy for the guard. But like you said, he left that for the medical school.”

“They’re not the same person,” Sans says. “But what’s your point?”

Red sinks back against the arm of the couch, staring at Sans as if with new eyes. “I’m a fucking idiot. I shoulda thought of this right off.”

“What?” Sans demands, sharper.

“That bastard had a pet project,” Red says. “He was trying to figure out how to induce soul cracks.”

The world goes slow. This couch, Red and Edge, his memories of the little paper cups of colorful pills, all caught in amber as his thoughts realign into something clear and cold. Grasping at the story he’d told himself for years, he says, “No. He wasn’t just some sadist. It wasn’t _pointless_. Why would he--”

“Dunno. The war, I figure,” Red says. “Humans have got souls too.”

Sans thinks of Gaster’s refusal to give him pain medication for all the necessary procedures that might not have been necessary at all. The mind games Gaster played with him even after he moved out. The smile on Gaster’s face as he fell into the Core, that moment before Sans’s soul cracked the first time. The way Gaster shoved him to Edge and Red’s universe to break again and nearly Fall. 

(Those vivid dreams about Gaster trying to pull the soul from his chest.)

Distantly, Sans feels Red take the cigarette that he’s about to drop on the couch. He touches his chest, the cold ache that lingers even after everything Edge did for him tonight, every bit of comfort he finds in Papyrus, every moment of pleasure in Red’s bed.

Still an experiment, even when he thought he’d gotten out. Until he dies or Gaster does, he’s a lab rat.

Despair is an old friend by now. He wears it like a security blanket, the bitterness of knowing that he can’t change things even if he tries. He expects its familiar weight to bury him, but what comes instead is a rage that there’s no words for. The guilt, the helplessness, the fear, the pain that Gaster’s inflicted on him and his brother, it all catches fire. He wants to tear the void’s throat out.

“Well,” Sans says, half-laughing. Edge’s hand presses harder on his back as if to hold him together, and Red looks at him like he sees the world burning and he isn’t sure whether to try to stop it or just stand back and enjoy the view. “Ain’t that a bitch.”

Is this what Red feels like all the time? Sans can see the appeal. It’s better than despair. Fuck it. Just drag Gaster out of the void and try to kill him. He’s already got blood on his hands. Why not spill a little more? Why the fuck not?

Because Gaster will kill them all.

That dumps cold water on the anger real quick. It doesn’t go out, not all the way. It’s still burning deep, like a vein of coal that caught fire and seethes underground. But he can think. He has to think. 

Sans takes a few deep, slow breaths, getting his shit together. More or less, anyway. When he can’t feel his pulse beating dully in his temples anymore like the drums of war, he tells Red, “I’m over it. Give me my cigarette back.”

Red does. “That was fast. Shame. You’re pretty when you’re thinking about murder.”

Sans turns back to Edge, who watches him warily. If they ever do this tragic backstory reveal bullshit again, he’s going to make them sit so he can see them both at the same time and doesn’t have to crane his head around every two seconds. “You’re the one who’s been all up close and personal with my soul, edgelord. You think he’s right?”

“I don’t know. Your soul seems no different to me than my brother’s, and I don’t remember the doctor so I can’t speak to his character,” Edge says. Steel slips into his voice, and it pulls an involuntary shiver out of Sans despite everything because his libido is fucking stupid. “It doesn’t change the fact that whatever his intentions, we’re going to kill him for what he’s done.”

“You’re goddamn right we are,” Red says quietly.

It’s probably fucked up to feel touched by that, but Sans does. He shakes his head and gives up on his cigarette, putting it down to smolder in the remains of its brethren. Red takes the ashtray and sits it on the floor, out of the way. “We don’t even know if he can die. If a fall into the Core didn’t do it--”

“Everything can die,” Red says. “It just takes creative thinking and a lot of explosives.”

Sans feels a rush of unfortunate fondness for him, sitting there grinning with visions of mayhem clearly dancing in his fucked up head. “Nice t-shirt slogan, buddy, but that’s a little over-optimistic. My point is that we don’t know what we’re dealing with. If you go in there half-cocked--”

Red readjusts himself. “Fully cocked, thank you very fucking much.”

Sans stares at him for a second, train of thought derailed by wondering if Red actually formed a dick just to make that joke, and decides he doesn’t want to know. “It’s too big a risk. Let him cool his heels in the void for a while. A long while. Taking the bus sucks, but it’s better than dragging him out here and getting all of you killed for nothing.”

“Not for nothing,” Edge says. When Sans turns back to him, the look in his eyes is a gutpunch. It’s goddamn unfair for Edge to look at him like he loves him.

(Edge loves him.)

Averting his eyes, Sans says, “Yeah, well. I appreciate the thought, but revenge isn’t worth your life either.”

“That’s not entirely my point,” Edge says. “That nightmare you had. That you’ve _been_ having, if I had to guess. Are you sure it’s only that? It seemed… unusually vivid.”

Sans shrugs. He’s had nightmares about Gaster for most of his life, but the ones after he ran into Gaster in the void (after Gaster touched him) have been different. He’s never been a lucid dreamer, but the nightmares are burned into his brain like actual memories. He’s never talked in his sleep, but apparently he’s gotten real chatty lately.

And then there’s the fact that the collar seems to ward the nightmares off. That could be proof in either direction, that this is all in his head and the collar is a crutch to let him sleep too deeply to dream or that Gaster is indeed playing Freddy Krueger and Edge’s protection is blocking him somehow.

“Dunno. Answer unclear. Try again later,” Sans says. “For now, it’s not gonna kill me to have a couple bad dreams.”

“Sleep deprivation and intense stress with an already damaged soul--” Edge begins.

“It doesn’t happen every night,” Sans says.

“Oh, then that makes it fine that the motherfucker is poking around in your head,” Red says.

“You think that’s my idea of a good time?” Sans snaps, turning to glare at Red. He feels like the ball being smacked around in a tennis match. “You think that’s fun for me? Nope! But it’s better than losing one of you. I can handle this. It doesn’t happen when I’m wearing--”

The collar.

Sans stalls out. Red, the bastard, grins slow and sharp. After a moment, Edge asks, “Sans?”

Thank fuck Sans has his head turned so Edge can’t see his expression. He clears his throat. “I’ve been sleeping in Red’s jacket. It helps.”

“That’s adorable,” Red says. “It’s not enough to convince anybody not to drag that asshole out of the void ASAP, but the mental picture is cute as a fucking button.”

Weirdly, it’s a relief that Red is giving him shit. It’s still infuriating as fuck, especially because Red’s right about him not convincing Edge, but at least it’s familiar bullshit.

“I’m glad it helps,” Edge says, and Sans turns back to him so he doesn’t have to watch Red smirk. It’s weird going between Red’s smugness and Edge’s worried sincerity, like going between a sauna and a bathtub full of ice. “But that isn’t a permanent solution.”

“No, I know,” Sans says. “I get that. It’s a stopgap until we come up with a decent plan that isn’t just hope and plastic explosives. When somebody figures out how to even plan anything when we don’t know if he’s eavesdropping, then we’ll talk.”

“A decent plan doesn’t involve trusting that a jacket will protect you from whatever he may be trying to do,” Edge says.

Sans spreads his hands. “Look, they may only be nightmares. It might be nothing. I’ve probably just got PTSD.”

Red snorts. “Y’think?”

“If anyone was in danger but you, you’d see that that’s not an acceptable risk,” Edge says. “To tell the truth, I’m not entirely comfortable with my brother using shortcuts when the doctor is waiting in the void.”

“Dude, don’t drag me into this,” Red says, an edge in his voice. “My magic’s working just fine. You’re not sticking me on a fucking _bus_.”

“My point,” Edge says, ignoring him, “is that the four of us are incredibly intelligent. We could come up with something as soon as tomorrow night.”

“Whoa, whoa, whoa,” Sans says. This is escalating out of control. “Let’s not get stupid here. My soul’s still fucked up, which means my magic’s on the fritz, which means I probably can’t fight. Not that I’m even real good at fighting in the first place. Red’s LV is acting up. This isn’t a good time.”

“We’ll wait until he’s recovered,” Edge says. “That should only be a few days. Maybe a week.”

“We don’t know what we’re doing,” Sans says. “The doctor survived a fall into the Core. He’s got enough power to shove us to another universe. That’s Frisk level trouble, and I for one suggest that we don’t poke it with a stick.”

“Just letting him torture you is not an acceptable alternative!” Edge shoots back.

Fuck it.

“How about this?” Sans pulls the collar out of his inventory and holds it out. It feels right in his hand, a wash of comfort settling his nerves. “Does this work better for you than the rocks fall, everyone dies plan?” 

He might as well have hauled off and slapped Edge in the face. Stunned into silence, Edge stares at him, eyes wide and dark and strangely vulnerable, then at the collar.

After a moment, Red says, “I think you broke him.”

“I’ve been wearing it,” Sans says because Edge continues not to say anything at all. “Uh. It helps me sleep. Makes me feel safe, I guess. I don’t have nightmares. I think maybe he can’t get to me when I’m in it.” Still nothing. “So. That’s a thing.” Yep, still dead silence. “I was lying about the jacket.”

“Well, there goes that spank bank fantasy,” Red sighs. He reaches around Sans and jabs Edge in the shoulder. “Boss.”

“Yes,” Edge says, jolted into it. “I mean. Good. I didn’t know you were…”

He trails off, looking a little helpless.

“Not around my neck,” Sans says, because that completely arbitrary line seems incredibly important suddenly. “Around my wrist.”

“That’s fine,” Edge says. “You’re wearing it.”

There’s something raw and wondering about the way he says that. All Sans’s careful plans about experiments and Schroedinger’s dates before he does anything that could get Edge hurt just became irrelevant. To Edge, this is a bigger deal than fucking him. This is serious.

Not the time to freak out about that. Definitely not the time.

“Does this work as a plan?” Sans asks, giving the collar a little shake for emphasis.

Edge shakes his head like a boxer who just took a punch and clears his throat, clearly trying to get his serious face back on. “You’re not having those nightmares with it on?”

“Not unless I take it off,” Sans says. “Which I won’t. Give me some more time to get fixed up before we do anything crazy. Maybe six months.”

“Three months,” Edge says, immediately quashing Sans’s hopes that he’s feeling so warm and fuzzy that he’ll agree to anything short of five years. “If you promise me that you’ll tell me if the collar stops working.”

“Five months,” Sans says.

“Hope you’re happy, boss.” Red presses a kiss to Sans’s shoulder. “This is the bullshit you’re signing up for all the time.”

“I’m aware,” Edge says, one of his almost-smiles tugging at his mouth. It fades. “Three months is the longest I’m willing to wait to deal with this. Take it or leave it.”

“Four months it is,” Sans says. When Edge’s eyes spark with genuine anger, he holds his hand up. “I’ll take what I can get. I still think this whole idea is fucking stupid.”

“You’ve made that clear, yes,” Edge says. “Now give me your word that you’ll tell me if the situation changes.”

Sans grimaces. “I’m not so great with promises--”

“Please,” Edge says.

“Fuck, that’s dirty pool,” Sans says, feeling that one word like a hand tight around his soul. Edge shrugs, not looking particularly sorry, and Sans sighs. “Okay. I promise. Happy?”

Edge glances at the collar and says with quiet honesty, “Yes.”

God. Showing him that collar was either the best or worst decision of Sans’s life, and he still doesn’t know which. Some stupid part of him is convinced that anything that puts that light in Edge’s eyes can’t be a mistake.

“Smart call taking his deal, sweetheart,” Red says. When Sans turns back to look at him, his eyes are half-lidded, his grin lazy. “My plan was to drag the fucker out and kill him right now.”

“Shitty plan,” Sans says. “Good thing you have Edge around to be your impulse control.”

“Truly my fate,” Edge says. “To forestall the worst of his terrible decisions.”

“Meh. Tonight. Three months. Doesn’t really matter. I’m gonna kill him.” It’s the same tone Red uses when he’s fucking Sans, moving inside him slow and sweet. “And when it’s done, I’ll lay his dust at your feet.”

“Fuck,” Sans says, appalled by the hot, perverse way that made his soul lurch. His wires must be crossed. When he glances at Edge for help, Edge is considering his brother with a deeply thoughtful look in his eyes. Sans returns his attention to Red. “That’s a weird kink even for you. And you should save half the pile for Paps.”

“I figured he wouldn’t appreciate it, what with his whole ‘no killing’ thing,” Red says. “I’ll give him the doc’s teeth instead.”

“Maybe just get him a gift card.” Sans drags a shaky hand over his face and asks a little plaintively, “Can we be done?”

“Yeah, we’re done,” Red says with unexpected mercy. “Unless the boss has more questions.”

“No,” Edge says. “You look like shit.”

“Thanks,” Sans says. “And here I thought confession was supposed to be good for the soul.”

“Fuck confession,” Red says, his voice hard. “ _He_ did this. It isn’t on you.”

Sans is too fucking tired to argue about it. He doesn’t look at Red, just asks Edge, “You mind driving me home?”

“No, of course not,” Edge says, snapping back to reality. “If that’s what you want.”

“You could always stick around,” Red says. Sans does turn to look at him then, and Red’s expression is something uncomfortably close to a plea. “Got a shitty mattress with your name on it. There’s breakfast in it for you.”

Whatever he and Red are to each other, Sans knows he’s one of Red’s people. Red, the territorial bastard, is already riding the edge of another breakdown, and here Sans is telling him that not only did Gaster hurt him and Papyrus, Gaster tried to get to him in Red’s home. And now Sans is bleeding from half a dozen emotional wounds and says that he wants to leave for somewhere that neither of them can keep an eye on him.

“Brother,” Edge begins carefully when Sans doesn’t say anything.

“Fine,” Sans says. After all the lines he’s crossed tonight, what’s one more? Red visibly uncoils, his grin losing some of its awful tension, and Sans adds, “You’re not getting laid, so just banish that thought from your horny little mind.”

“Aw, no sweet, sweet comfort sex?” Red asks.

“Weirdly, talking about this shit doesn’t get me hot,” Sans says. “I’m beat. I just wanna sleep.”

That comes out slightly more bleak than he intended it to. He can’t lie to himself and say that he’s staying entirely out of concern for Red’s mental state. The thought of going home and trying to sleep alone makes his throat feel tight. A warm, familiar body pressed up against him in the dark sounds pretty good right now.

“Yeah, honey,” Red says, quiet. “We can do that.”

Sans exhales, then turns to Edge. “Then I’ll crash here tonight if that’s cool with you, edgelord.”

Edge gives him a look that says he’s adorable but terribly dense, which is probably fair. Part of Sans’s whole commitment-phobic problem, the reason for all these experiments in the first place, is that Edge doesn’t seem like the kind of guy who only wants Sans in his bed long enough to fuck him before politely asking him to let himself out. But inviting himself over without so much as a how do you do is fucking rude and Sans was raised in a lab, not a barn. 

“Of course,” Edge says. He nods at the collar. “May I see that for a moment?”

Sans’s instinctive response is _no, mine now, no take-backs._ He decides to blame it on the fact that he’s tired. He holds it out, Edge takes it, and he tries to ignore the way the anxiety and old scars get louder like a radio station coming back into range.

He climbs off the couch, his body aching like he survived a beating instead of just a hard conversation. Having his soul healed last time left him feeling warm and sated, like having a great meal, an amazing fuck and then sleeping in a sunbeam all afternoon. Apparently Gaster undid a good chunk of Edge’s hard work in one nightmare. Figures.

Red’s watching him, getting tenser the closer Sans gets to the door until Sans pulls his cell out of his pocket and holds it up. “Just gotta text Paps. Cool your tits.”

“Fuck you. My tits are frosty,” Red says. “My nipples could cut glass, they’re so chill.”

“You look it,” Sans says. “What with the way your eye is twitching.”

Red gives him the finger. Sans turns his attention to his phone, tapping out a quick text to Papyrus. _u ok if i stay over at red’s 2nite?_

Almost instantly, Papyrus replies with, _I AM A FUNCTIONAL ADULT WHO ONLY SETS THINGS ON FIRE WHEN UNDYNE IS HERE. I’LL BE FINE IF YOU STAY WITH YOUR BONEFRIEND. ALSO, PLEASE STAND BY FOR A STRING OF WINKING, SUGGESTIVE EMOJIS._

Papyrus is as good as his word. It’s kind of amazing how many emojis he can send in the span of thirty seconds. Sans waits it out, then texts, _k. cu tomorrow. plz delete the eggplant emoji off ur phone._

_DO NOT DENY ME MY NIGHTSHADES. GOOD NIGHT, BROTHER._

Well, that’s handled. Sans drops his phone back in his jacket pocket and looks up to find that Edge has his eyes closed and the collar cupped in his hands. There’s a red glow between his fingers, the same as when he pours magic into Sans’s soul. Must be adding another layer of protection to the collar. Smart, considering that it might be the one thing warding Gaster off, if Gaster even needs to be warded off and Sans isn’t just losing his goddamn mind. 

Red pats his thigh, inviting Sans to come park it on his lap, and shrugs like _hey, your loss_ when Sans sits on the couch instead. “Should just be a minute. He fucks with mine all the time, the paranoid bastard.” 

“You were hardly better when I was the one in the collar.” Edge opens his eyes, the glow of his magic fading out. He looks tired but satisfied. “There. May I have your wrist?” 

Sans obliges him. Edge’s hands are gentle, painfully careful, as he wraps the collar around Sans’s wrist. He examines the result, pausing to slip a fingertip between the collar and Sans’s ulna, testing the fit before he nods. 

“Quit playing ‘just the tip’ and buckle it already,” Red says, leaning over Sans’s shoulder to get a good view. 

Edge gives him a Look, glances at Sans, and looks away. There’s that faint blush across his cheekbones again. He closes the buckle with practiced fingers and then just sits there, Sans’s wrist cradled in his warm hands. 

“Thank you,” Edge says, meeting his eyes. Small words, but the look in Edge’s eyes is something too big for Sans to take in at once. ( _That’s what she said,_ he thinks, and almost ruins this tender moment by laughing like a crazy person.) Edge runs the pad of his thumb over the collar, brushing the sensitive inside of his wrist, and heat rolls through Sans like a shudder. “This means a great deal to me.” 

“Neat,” Sans says stupidly. Red has the unexpected tact to muffle his sniggering against Sans’s shoulder. “I mean. Yeah. Thanks for giving it to me.” 

The unintentional double entendre catches up to him a couple seconds too late, but Edge has already let him go at that point. Sans pulls his wrist into his lap, his other hand curling around it. He can still feel the warmth of Edge’s touch. Before things can get any more confusing, he says, “Welp, it’s been a long, crazy night. I should sleep. Sorry for screaming my head off and stabbing you in the chest.” 

Edge shakes his head. “It’s already healed. No permanent harm done. Honestly, you have no idea how reassuring I find it that your first impulse was to defend yourself.” 

“I could’ve just told you that,” Sans says. “No need to give such a pointed demonstration. Knife of you to say so, though. Shanks.” 

Edge sighs from the depths of his soul, a smile tugging at the corner of his mouth. “If you keep reaching for puns from the bottom of the barrel, you’ll only exhaust yourself further. Take him to bed, brother. If you need me, I’ll be out here.” 

Speaking of things that are more reassuring than Edge will ever know. Sans nods wearily, shrugs Red’s chin off his shoulder and gets up. “Good night, John Boy. See you in the morning.” 

“What the fuck is a John Boy?” Edge asks, frowning. 

“Juvenile form of a John Man, obviously,” Red says. He curls an arm around Sans’s hips and pulls him towards his bedroom as if Sans wasn’t already going in that direction. He doesn’t tell Edge good night. “C’mon, sweetheart.” 

Red steers Sans to his bedroom and closes the door. It’s dark, illuminated only by Red’s eyelights and the light in from the streetlights outside, slanting through the blinds. It’s a warm, welcome dark, as unlike the void as it could be, and Sans relaxes into it and lets it catch him. 

“Take your clothes off,” Red says, tugging at Sans’s shirt. It sticks to Sans’s ribs a little. He sweated through it during that nightmare, cold fear sweat. “You can borrow my stuff to sleep in.” 

Sans is too tired to put up a bullshit fight just for the sake of it. He peels his clothes off and puts on the ones Red offers him, some worn-soft t-shirt for a band that Sans doesn’t recognize and a pair of old shorts. Red changes into sleep clothes of his own, which are basically indistinguishable from the stuff that he wears out of the house. Then he bullies Sans into bed. 

When Sans curls up on his side, Red snuggles in behind him, a protective arm draped over his belly, pulling him back against the solid warmth of Red’s body. Sans stares at the wall and doesn’t blink no matter how much his eyes burn. Apparently co-sleeping is his emotional kryptonite. Who knew? 

Red presses a kiss to his neck. It’s aimless affection, nothing particularly sexual about it. His breath is warm on Sans’s spine, a reminder that Sans is here and safe and not alone. Sans realizes distantly that he’s shaking, a shocky feeling like the aftermath of blowing through too much magic at once. Stupid. All he did was talk. 

“Hey,” Red murmurs. Sans tenses because if Red starts being nice to him right now, he’s pretty sure he’s going to flip his shit, but Red only asks, “You like waffles? Or are you more of a pancake kind of guy?” 

Sans blinks, trying to puzzle out what the fuck Red is going on about, and then realizes it’s about breakfast tomorrow morning. “I’m not really that picky.” 

“That’s news to me,” Red says. Sans snorts, a watery noise, and Red’s arm tightens a little around him. “Well, I’m in the mood for some goddamn pancakes. With chocolate chips.” 

“Should go great with ketchup,” Sans says. 

“Even I think that’s disgusting,” Red says. “Mustard or nothing.” 

“That’s fucked up.” 

“ _You’re_ fucked up.” The easy call and response of bullshit lets Sans breathe a little easier. He’s aware he’s being manipulated. He just doesn’t care. Red gives another kiss to the back of his neck. “You two can do the whole stupid dance of not technically offering food tomorrow. It’ll be hilarious. Now get some sleep.” 

Sans is exhausted, a heaviness he can feel in his eyelids and his soul, but now that he’s actually in a bed, he’s too twitchy to do anything about it. He hesitates, then sighs. “Red?” 

“Still here,” Red says. “Didn’t go anywhere in the last five seconds.” 

This is opening the door to endless mockery for the rest of their lives, but Sans says, “Might be okay if you talked to me for a while. Get some of the bullshit out of your system. I don’t want you to get word constipation.” 

“Thoughtful of you,” Red says. He shifts his weight, making himself comfortable. “Okay. Did I ever tell you about how my bro found that fucking hellbeast of his?” 

They both know Red hasn’t, but Sans says, “Nope. Haven’t heard that one.” 

“It’s pretty hilarious,” Red says. “So about five years ago, he’s on his way back from school when he almost trips on this snow poff…” 

Leaning back into Red, Sans closes his eyes and lets the words roll over him until they stop meaning anything. He’s only faintly aware of taking Red’s hand, twining their fingers together. He holds on. 

**Notes for the Chapter:**

> Content warnings: Hoo boy. This chapter is rough. Sans has another nightmare about Gaster nonconsensually touching his soul and accidentally stabs Edge in a blind panic, references to Edge being forced to torture Red in Underfell and UF!Asgore turning prisoners over to be experimented on, Red briefly and incorrectly assumes that Gaster might've raped Sans, Sans makes excuses for Gaster as a result of Gaster's gaslighting, a lot of references to Sans and Papyrus's history of childhood medical abuse including a mention of vomiting and a detailed flashback to a medical procedure without anesthetic, reference to Sans being occasionally suicidal during his time with Gaster, a lot of Red and Edge talking about murdering Gaster slowly, references to Red prostituting himself for food.
> 
> If you want to skip the detailed flashback to the medical procedure, it's the paragraph that starts with the line "The feeding tube has limited applications."


End file.
